Problem: $\dfrac{6}{5} - \dfrac{5}{8} = {?}$
$ = {\dfrac{6 \times 8}{5 \times 8}} - {\dfrac{5 \times 5}{8 \times 5}} $ $ = {\dfrac{48}{40}} - {\dfrac{25}{40}} $ $ = \dfrac{{48} - {25}}{40} $ $ = \dfrac{23}{40}$